Main drain closing question - did I do enough?

n240sxguy

Well-known member
May 17, 2014
1,802
Benton, KY
#1
I closed my pool about a week ago. I blew all the lines, and plugged them. I blew the skimmers, put a plug in one, and a gizmo in the other because I couldn't get a plug to work. I dropped the water level to just below the skimmers, vacuumed the water out of the skimmers, and put a jug in the one with the plug, and pool noodle pieces in both. I covered the skimmer lids with a piece of old liner to keep the rain from filling them up after i put antifreeze in each. When I tried to blow the main drain, it never bubbled. I shut the valve on the main drain, turned off the blower, then opened the valve back, and could hear air coming back out from the water pushing back into the main drain. I poured two gallons of antifreeze into the main drain and turned the blower back on. I never saw pink coming out of the main drain. I closed the valve and figured the amount of air I pushed back down the main drain, plus the two gallons of antifreeze would be plenty to keep it from freezing. Anyone agree or object to this? I would've used my compressor to blow the main drain, but its 240v, and I would either need to make a 150ft extension cord, rig up something at the pool pad, get another 100ft of air hose, or drag it all the way to the pool and use what air was in the tank to blow the line. None of which would be an easy task. What say ye?
 

pooladdict

TFP Guide
In The Industry
May 14, 2007
819
New Brunswick Canada
#2
Exactly what most would do. The water in that main line can freeze, but it now can grow up the line and cause no damage. Companies in my area do not blow out main drains at all. The ball valve will leak as you saw. I go one step further, I use a cyclone and blow the main completely free of water, close valve, then add a pressure plug. This guarantees the air will keep the water from coming back up the line again.
 

n240sxguy

Well-known member
May 17, 2014
1,802
Benton, KY
#3
The air didn't come back out until I opened the ball valve. No way to know if the valve actually seals good or if it would have a slow leak over time and allow the water back in that line. I didn't do the math, but on a 2" line, i didn't figure it would hold more than 8 to 10 gallons of water. I displaced 2 with antifreeze and maybe another 2 with air. I could talk to the previous owner and see if he even blew that line when he closed it.


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n240sxguy

Well-known member
May 17, 2014
1,802
Benton, KY
#5
The plug would be hard to do on my setup. The main drain has a double union ball valve then t's into the manifold that goes to the pump. No good place to plug it.


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n240sxguy

Well-known member
May 17, 2014
1,802
Benton, KY
#7
I didn't realize there was that much room there. Didn't think it looked like it at the time. I'll save that trick for next year and maybe get a portable air tank to blow it out with. With pressure and gravity on my side I should be able to get out 90+% of the water then hold that air lock with the valve and plug.


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